Introduction to Trilaminar Embryology Flashcards
1
Q
What is competence and what does it require?
A
- Capacity of responder cells to respond to induction
- Requires activation of responding tissue by competence factor
2
Q
What are the two functions. of the cortex of the ovary?
A
- OOGENESIS
- FOLLICULOGENESIS
3
Q
Describe follicle maturation.
A
- Essential for ovulation
- Caused by surge in FSH
4
Q
Describe the appearance of follicle cells.
A
PRIMORDIAL FOLLICLE - squamous
PRIMARY FOLLICLE - cuboidal
LATE PRIMARY - stratified
5
Q
What occurs in phase 1 of fertilisation?
A
- Capacitation of sperm
- Glycoprotein coat and plasma membrane proteins removed from acrosomal region
- Penetration of corona radiata
6
Q
What occurs in phase 2 of fertilisation? PART 1
A
- Sperm binds to zona pellucida
- Release of acrosin and trypsin
7
Q
What occurs in phase 2 of fertilisation? PART 2
A
- Once head of sperm breaks through zona pellucida, enzymes released from oocyte plasma membrane
- Enzymes alter properties of zona pellucida, prevent entry of any other sperm
8
Q
Describe phase 3 of fertilisation.
A
- Sperm leaves plasma membrane on oocyte surface. Male pronucleus forms.
- Oocyte completes 2nd meiotic divsion to form 2nd polar body. Female pronucleus forms
- Pronuclei fuse
8
Q
What occurs around day 6?
A
- Capture of blastocyst from uterine cavity
- L-selectins attach to carbohydrate receptors on uterine epithelium.
- Trophoblast integrins stimulate laminin and fibronectin development - causes further implantation
9
Q
What are some abnormal sites of implantation and what are the consequences?
A
- Abdominal cavity, ovary and fallopian tube
- Can cause ectopic/extrauterine pregnancy
10
Q
What occurs in day 9?
A
- Blastocyst deeply buried in endometrium
- Flattened hypoblast cells form Heuser’s membrane which lines exocoelomic cavity/primitive yolk sac
- Vacuoles form lacunae in syncytium
11
Q
What occurs in days 11-12? PART 1
A
- Blastocyst completely embedded
- Syncytiotrophoblast cells erode congested maternal capillaries
12
Q
What occurs in days 11-12? PART 2
A
- Lacunae become continuous with sinusoids
- Maternal blood enters lacunar system - uteroplacental circulation
13
Q
What occurs in days 15-16?
A
- Primitive streak present on surface of epiblast
- Primitive node develops at cephalic end of streak
- Epiblastic cell invaginate through streak - using FGF8
14
Q
What is the notochord?
A
- Formed in cranial region and develops caudally
- Signalling centre for FGF, TGF and Wnt
